The present invention relates to a controller for a printer, including a first sensor which generates a reference signal for feeding and discharging recording paper, and a second sensor which generates a reference signal for the printing operation.
A conventional controller for a printer functions so that overlay-recording a plurality of times corresponding to the number of turns of rotation of a drum is performed on recording paper as the paper is secured on the drum. The printer comprises the drum which is rotated with the recording paper secured thereon, a thermal head which performs printing in accordance with a printing signal, an ink donor film having ink layers with a plurality of colors for transfer to the recording paper, a control section for controlling the rotation of the drum, etc., a securing section for securing the recording paper on the drum, and a paper feed/discharge unit. When the recording paper secured on the drum reaches the position of the thermal head, the heaters of the thermal head are heated in response to the printing signal sent from the control section to the thermal head. This melts the ink on the ink donor film to transfer the ink to the recording paper. For color overlay-printing, the drum is rotated by one turn after printing in one color. This brings the recording paper to the position of the thermal head again, and aligns the foremost part of the next color in a proper position to print in the next color. The control is performed by detecting the position of the drum with an encoder or a sensor, which is provided in the home position of the drum. Such controlled printing is sequentially repeated to complete the color overlay-print.
Although the conventional controller employing an encoder has a high accuracy, the controller also has a high cost. Although the conventional controller employing the sensor provided in the home position of the drum is less expensive, this controller does not have a very high accuracy.